Damage to mitochondria. Mitochondrial toxicity may affect different parts of the body, including the heart, nerves, muscles, pancreas, kidneys, and liver. Conditions resulting from mitochondrial toxicity can include muscle weakness, inflammation of the pancreas (pancreatitis), high levels of lactic acid in the blood (lactic acidosis), changes in distribution and amount of body fat (lipodystrophy), and fatty liver (hepatic steatosis). Use of certain antiretroviral (ARV) drugs may cause mitochondrial toxicity.